1. Field of the Invention
The present invention relates to an automatic transmission primarily intended for motor vehicle use, and more particularly, to a method of controlling the release element during a coastdown shift for a transmission that is controlled electronically and hydraulically.
2. Description of Related Art
Generally speaking, land vehicles require three basic components. These components comprise a power plant (such as an internal combustion engine) a power train and wheels. The internal combustion engine produces force by the conversion of the chemical energy in a liquid fuel into the mechanical energy of motion (kinetic energy). The function of the power train is to transmit this resultant force to the wheels to provide movement of the vehicle.
The power train's main component is typically referred to as the "transmission". Engine torque and speed are converted in the transmission in accordance with the tractive-power demand of the vehicle. The vehicle's transmission is also capable of controlling the direction of rotation being applied to the wheels, so that the vehicle may be driven both forward and backward.
A conventional transmission includes a hydrodynamic torque converter to transfer engine torque from the engine crankshaft to a rotatable input member of the transmission through fluid-flow forces. The transmission also includes frictional units which couple the rotating input member to one or more members of a planetary gearset. Other frictional units, typically referred to as brakes, hold members of the planetary gearset stationary during flow of power. These frictional units are usually brake clutch assemblies or band brakes. The drive clutch assemblies can couple the rotating input member of the transmission to the desired elements of the planetary gearsets, while the brakes hold elements of these gearsets stationary. Such transmission systems also typically provide for one or more planetary gearsets in order to provide various ratios of torque and to ensure that the available torque and the respective tractive power demand are matched to each other.
Transmissions are generally referred to as manually actuated or automatic transmissions. Manual transmissions generally include mechanical mechanisms for coupling rotating gears to produce different ratio outputs to the drive wheels.
Automatic transmissions are designed to take automatic control of the frictional units, gear ratio selection and gear shifting. A thorough description of general automatic transmission design principals may be found in "Fundamentals of Automatic Transmissions and Transaxles," Chrysler Corporation Training Manual No. TM-508A. Additional descriptions of automatic transmissions may be found in U.S. Pat. No. 3,631,744, entitled "Hydromatic Transmission," issued Jan. 4, 1972 to Blomquist, et al., and U.S. Pat. No. 4,289,048, entitled "Lock-up System for Torque Converter," issued on Sep. 15, 1981 to Mikel, et al. Each of these patents is hereby incorporated by reference.
In general, the major components featured in such an automatic transmission are: a torque converter as above-mentioned; fluid pressure-operated multi-plate drive or brake clutches and/or brake bands which are connected to the individual elements of the planetary gearsets in order to perform gear shifts without interrupting the tractive power; one-way clutches in conjunction with the frictional units for optimization of power shifts; and transmission controls such as valves for applying and releasing elements to shift the gears (instant of shifting), for enabling power shifting, and for choosing the proper gear (shift point control), dependent on shift-program selection by the driver (selector lever), accelerator position, the engine condition and vehicle speed.
The control system of the automatic transmission is typically hydraulically operated through the use of several valves to direct and regulate the supply of pressure. This hydraulic pressure control will cause either the actuation or deactuation of the respective frictional units for effecting gear changes in the transmission. The valves used in the hydraulic control circuit typically comprise spring-biased spool valves, spring-biased accumulators and ball check valves. Since many of these valves rely upon springs to provide a predetermined amount of force, it will be appreciated that each transmission design represents a finely tuned arrangement of interdependent valve components. While this type of transmission control system has worked well over the years, it does have its limitations. For example, such hydraulically controlled transmissions are generally limited to one or a very small number of engines and vehicle designs. Therefore, considerable cost is incurred by an automobile manufacturer to design, test, build, inventory and repair several different transmission units in order to provide an acceptable broad model line for consumers.
Additionally, it should be appreciated that such hydraulically controlled transmission systems cannot readily adjust themselves in the field to compensate for varying conditions such as normal wear on the components, temperature swings and changes in engine performance over time. While each transmission is designed to operate most efficiently within certain specific tolerances, typical hydraulic control systems are incapable of taking self-corrective action on their own to maintain operation of the transmission at peak efficiency.
However, in recent years, a more advanced form of transmission control system has been proposed, which would offer the possibility of enabling the transmission to adapt itself to changing conditions. In this regard, U.S. Pat. No. 3,956,947, issued on May 18, 1976 to Leising, et al., which is hereby incorporated by reference, sets forth a fundamental development in this field. Specifically, this patent discloses an automatic transmission design which features an "adaptive" control system that includes electrically operated solenoid-actuated valves for controlling certain fluid pressures. In accordance with this electric/hydraulic control system, the automatic transmission would be "responsive" to an acceleration factor for controlling the output torque of the transmission during a shift from one ratio of rotation (between the input and output shafts of the transmission) to another. Specifically, the operation of the solenoid-actuated valves would cause a rotational speed versus time curve of a sensed rotational component of the transmission to substantially follow along a predetermined path during shifting.
3. Objects Of The Present Invention
It is one of the principal objects of the present invention to provide a significantly advanced electronically controlled transmission which is fully adaptive. By fully adaptive, it is meant that substantially all shifts are made using closed-loop control (i.e., control based on feedback). In particular, the control is closed loop on speed, speed ratio, or slip speed of either N.sub.t (turbine) of the torque converter and N.sub.e (engine) or a combination of N.sub.t and N.sub.o (output) which will provide the speed ratio or slip speed. This transmission control is also capable of "learning" from past experience and making appropriate adjustments on that basis.
Another object of the present invention is to provide an automatic transmission in which the shift quality is maintained approximately uniform regardless of the engine size, within engine performance variations or component condition (i.e. the transmission control system will adapt to changes in engine performance or in the condition of the various frictional units of the transmission).
It is a more specific object of the present invention to provide a method of controlling the release element during a coastdown shift whenever slip is detected.
It is a further object of the present invention to achieve exceptionally smooth, yet quick kickdown shifts (i.e., second to first gear), and in so doing, make any powertrain feel more responsive without increasing harshness. Being adaptive, these controls will be capable of compensating for changes in engine or frictional element torque, and provide consistent shift quality over the life of the transmission.
This application is one of several applications filed on the same date, all commonly assigned and having similar Specification and Drawings, these applications being identified below.
__________________________________________________________________________ U.S. Ser. No. Title __________________________________________________________________________ 187,772, now U.S. Pat. AN ELECTRONICALLY-CONTROLLED No. 4,875,391 ADAPTIVE AUTOMATIC TRANSMISSION SYSTEM 187,751, now U.S. Pat. No. AUTOMATIC FOUR-SPEED TRANSMISSION 189,493, now U.S. Pat. PUSH/PULL CLUTCH APPLY PISTON OF AN No. 4,915,204 AUTOMATIC TRANSMISSION 187,781, now SHARED REACTION PLATES BETWEEN abandoned CLUTCH ASSEMBLIES IN AN AUTOMATIC TRANSMISSION 189,492, abandoned in CLUTCH REACTION AND PRESSURE PLATES favor of IN AN AUTOMATIC TRANSMISSION U.S. Ser. No. 432,311, now U.S. Pat. No. 4,958,753 188,602, abandoned in BLEEDER BALL CHECK VALVES IN AN favor of U.S. AUTOMATIC TRANSMISSION Ser. No. 463,871, now U.S. Pat. No. 4,982,826 188,610, abandoned in PRESSURE BALANCED PISTONS IN AN favor of U.S. Ser. AUTOMATIC TRANSMISSION No. 488,419, now U.S. Pat. No. 4,969,506 189,494, now U.S. Pat. DOUBLE-ACTING SPRING IN AN No. 5,027,934 AUTOMATIC TRANSMISSION 188,613, now U.S. Pat. PARK LOCKING MECHANISM FOR AN No. 4,907,681 AUTOMATIC TRANSMISSION 187,770, now U.S. Pat. SOLENOID-ACTUATED VALVE ARRANGEMENT No. 4,887,491 OF AN AUTOMATIC TRANSMISSION SYSTEM 187,796, abandoned in RECIPROCATING VALVES IN A FLUID favor of U.S. Ser. SYSTEM OF AN AUTOMATIC TRANSMISSION No. 532,149, now U.S. Pat. No. 5,031,656 187,705, now U.S. Pat. VENT RESERVOIR IN A FLUID SYSTEM OF No. 4,887,512 AN AUTOMATIC TRANSMISSION 188,592, now U.S. Pat. FLUID ACTUATED SWITCH VALVE IN AN No. 4,936,166 AUTOMATIC TRANSMISSION 188,598, now U.S. Pat. DIRECT-ACTING, NON-CLOSE CLEARANCE No. 4,893,652 SOLENOID-ACTUATED VALVES 188,618 NOISE CONTROL DEVICE FOR A SOLENOID-ACTUATED VALVE 188,605, now U.S. Pat. FLUID ACTUATED PRESSURE SWITCH FOR No. 4,871,887 AN AUTOMATIC TRANSMISSION 187,210 now U.S. Pat. METHOD OF APPLYING REVERSE GEAR OF No. 4,944,200 AN AUTOMATIC TRANSMISSION 187,672 TORQUE CONVERTER CONTROL VALVE IN A FLUID SYSTEM OF AN AUTOMATIC TRANSMISSION 187,120, abandoned in favor CAM-CONTROLLED MANUAL VALVE IN AN of U.S. Ser. No. AUTOMATIC TRANSMISSION 338,493, now U.S. Pat. No. 4,916,961 187,181, now U.S. Pat. FLUID SWITCHING MANUALLY BETWEEN No. 4,907,475 VALVES IN AN AUTOMATIC TRANSMISSION 187,704, now U.S. Pat. METHOD OF OPERATING AN ELECTRONIC No. 4,975,845 AUTOMATIC TRANSMISSION SYSTEM 188,020, now U.S. Pat. METHOD OF SHIFT SELECTION IN AN No. 4,935,872 ELECTRONIC AUTOMATIC TRANSMISSION SYSTEM 187,991, abandoned in favor METHOD OF UNIVERSALLY ORGANIZING of U.S. Ser. No. 320,883 SHIFTS FOR AN ELECTRONIC AUTOMATIC now U.S. Pat. No. TRANSMISSION SYSTEM 4,936,167 188,603, abandoned in favor METHOD OF DETERMINING AND of U.S. Ser. No. CONTROLLING THE LOCK-UP OF A TORQUE 470,439, now U.S. Pat. No. CONVERTER IN AN ELECTRONIC 4,993,527 AUTOMATIC TRANSMISSION SYSTEM 188,617, now U.S. Pat. METHOD OF ADAPTIVELY IDLING AN No. 4,965,728 ELECTRONIC AUTOMATIC TRANSMISSION SYSTEM 189,553 METHOD OF DETERMINING THE DRIVER SELECTED OPERATING MODE OF AN AUTOMATIC TRANSMISSION SYSTEM 188,615, now U.S. Pat. METHOD OF DETERMINING THE SHIFT No. 4,965,735 LEVER POSITION OF AN ELECTRONIC AUTOMATIC TRANSMISSION SYSTEM 188,594, now U.S. Pat. METHOD OF DETERMINING THE No. 4,947,329 ACCELERATION OF A TURBINE IN AN AUTOMATIC TRANSMISSION 187,771, now U.S. Pat. METHOD OF DETERMINING THE FLUID No. 4,928,235 TEMPERATURE OF AN ELECTRONIC AUTOMATIC TRANSMISSION SYSTEM 188,607, abandoned in favor of METHOD OF DETERMINING THE U.S. Ser. No. 366,361, CONTINUITY OF SOLENOIDS IN AN now U.S. Pat. No. ELECTRONIC AUTOMATIC TRANSMISSION 4,939,928 SYSTEM 189,579, now U.S. Pat. METHOD OF DETERMINING THE THROTTLE No. 4,975,844 ANGLE POSITION FOR AN ELECTRONIC AUTOMATIC TRANSMISSION SYSTEM 188,604, now U.S. Pat. METHOD OF CONTROLLING THE SPEED No. 4,905,545 CHANGE OF A KICKDOWN SHIFT FOR AN ELECTRONIC AUTOMATIC TRANSMISSION SYSTEM 188,591, now U.S. Pat. METHOD OF CONTROLLING THE APPLY No. 4,951,200 ELEMENT DURING A KICKDOWN SHIFT FOR ELECTRONIC AUTOMATIC TRANSMISSION SYSTEM 188,608 METHOD OF CALCULATING TORQUE FOR AN ELECTRONIC AUTOMATIC TRANSMISSION SYSTEM 187,150, abandoned in favor of METHOD OF LEARNING FOR ADAPTIVELY U.S. Ser. No. 496,144, CONTROLLING AN ELECTRONIC AUTOMATIC now U.S. Pat. No. TRANSMISSION SYSTEM 4,982,620 188,595 METHOD OF ACCUMULATOR CONTROL FOR A FRICTION ELEMENT IN AN ELECTRONIC AUTOMATIC TRANSMISSION SYSTEM 188,599, abandoned in favor of METHOD OF ADAPTIVELY SCHEDULING A U.S. Ser. No. 326,492, SHIFT FOR AN ELECTRONIC AUTOMATIC now U.S. Pat. TRANSMISSION SYSTEM No. 4,938,102 188,620, now U.S. Pat. METHOD OF TORQUE PHASE SHIFT No. 4,969,098 CONTROL FOR AN ELECTRONIC AUTOMATIC TRANSMISSION 188,596, now U.S. Pat. METHOD OF DIAGNOSTIC PROTECTION FOR No. 4,951,205 AN ELECTRONIC AUTOMATIC TRANSMISSION SYSTEM 188,597, now U.S. Pat. METHOD OF STALL TORQUE MANAGEMENT No. 4,991,097 FOR AN ELECTRONIC AUTOMATIC TRANSMISSION SYSTEM 188,606, now U.S. Pat. METHOD OF SHIFT TORQUE MANAGEMENT No. 4,968,999 FOR AN ELECTRONIC AUTOMATIC TRANSMISSION SYSTEM 188,616, now U.S. Pat. ELECTRONIC CONTROLLER FOR AN No. 4,998,200 AUTOMATIC TRANSMISSION 188,600, now U.S. Pat. DUAL REGULATOR FOR REDUCING SYSTEM No. 4,959,786 CURRENT DURING AT LEAST ONE MODE OF OPERATION 188,619, now U.S. Pat. UTILIZATION OF A RESET OUTPUT OF A No. 4,992,951 REGULATOR AS A SYSTEM LOW-VOLTAGE INHIBIT 188,593, abandoned in favor of THE USE OF DIODES IN AN INPUT U.S. Ser. No. 537,227, CIRCUIT TO TAKE ADVANTAGE OF AN now U.S. Pat. No. ACTIVE PULL-DOWN NETWORK PROVIDED 5,014,214 IN A DUAL REGULATOR 188,609, abandoned in favor of SHUTDOWN RELAY DRIVER CIRCUIT U.S. Ser. No. 541,450, now U.S. Pat. No. 4,991,096 188,614, now U.S. Pat. CIRCUIT FOR DETERMINING THE CRANK No. 4,955,336 POSITION OF AN IGNITION SWITCH BY SENSING THE VOLTAGE ACROSS THE STARTER RELAY CONTROL AND HOLDING AN ELECTRONIC DEVICE IN A RESET CONDITION IN RESPONSE THERETO 188,612, now U.S. Pat. THROTTLE POSITION SENSOR DATA No. 4,901,561 SHARED BETWEEN CONTROLLER WITH DISSIMILAR GROUNDS 188,611, abandoned in favor of NEUTRAL START SWITCH TO SENSE SHIFT U.S. Ser. No. 492,269, LEVER POSITION now U.S. Pat. No. 4,998,450 188,981, abandoned in favor of OPEN LOOP CONTROL OF SOLENOID COIL U.S. Ser. No. 492,235, DRIVER now U.S. Pat. No. 4,980,793 __________________________________________________________________________
Commonly assigned application Ser. No. 07/187,772, filed Apr. 29, 1988, now U.S. Pat. No. 4,875,391 will be printed in its entirety. The Figures and the entire Specification of that application are specifically incorporated by reference. For a description of the above copending applications, reference is made to the above mentioned U.S. Pat. No. 4,875,391.